This invention relates to new improved hydrophilic crosslinked polyurethane foams which simulate natural sponges and to a method for their preparation. More particularly, the present invention relates to hydrophilic foams prepared from a capped polyoxyethylene polyol reactant having a defined average reaction functionality greater than two, an aqueous reactant and a carefully balanced combination of a nonionic surface-active agent and a liquid defoaming agent.
Numerous attempts have been made in the prior art to produce hydrophilic polyurethane foams which simulate natural sponges. Typically, the product foams are either open-celled structures having membranes substantially intact or otherwise are reticulated with membranes substantially removed. By practice of the present invention, however, a foam is generated which more closely simulates natural sponges by having a majority of large cells and interconnecting membranes which themselves are foamed with very small cells. These improved new hydrophilic crosslinked polyurethane foams may be prepared simply by reacting a particular isocyanate capped polyoxyethylene polyol with an aqueous reactant and a carefully balanced combination of nonionic surface-active agent and a liquid defoaming agent.